/**
* @param array|float[] $a
* @param bool $sample
*
* @return float
*
* @throws InvalidArgumentException
*/
public static function population(array $a, $sample = true)
{
if (empty($a)) {
throw InvalidArgumentException::arrayCantBeEmpty();
}
$n = count($a);
if ($sample && $n === 1) {
throw InvalidArgumentException::arraySizeToSmall(2);
}
$mean = Mean::arithmetic($a);
$carry = 0.0;
foreach ($a as $val) {
$d = $val - $mean;
$carry += $d * $d;
}
if ($sample) {
--$n;
}
return sqrt((double) ($carry / $n));
}
/**
* @param array|int[]|float[] $x
* @param array|int[]|float[] $y
*
* @return float
*
* @throws InvalidArgumentException
*/
public static function pearson(array $x, array $y)
{
if (count($x) !== count($y)) {
throw InvalidArgumentException::arraySizeNotMatch();
}
$count = count($x);
$meanX = Mean::arithmetic($x);
$meanY = Mean::arithmetic($y);
$axb = 0;
$a2 = 0;
$b2 = 0;
for ($i = 0; $i < $count; ++$i) {
$a = $x[$i] - $meanX;
$b = $y[$i] - $meanY;
$axb = $axb + $a * $b;
$a2 = $a2 + pow($a, 2);
$b2 = $b2 + pow($b, 2);
}
$corr = $axb / sqrt((double) ($a2 * $b2));
return $corr;
}
public function testModeOnArray()
{
$numbers = [5, 2, 6, 1, 3, 4, 6, 6, 5];
$this->assertEquals(6, Mean::mode($numbers));
}
/**
* @param array $currentAxis
*
* @return float|mixed
*/
public function replaceValue(array $currentAxis)
{
return Mean::mode($currentAxis);
}
/**
* @param array $currentAxis
*
* @return float
*/
public function replaceValue(array $currentAxis)
{
return Mean::arithmetic($currentAxis);
}
